The present invention relates to a fuel inlet for pouring fuel into a fuel tank of a car and the like, and a manufacturing method thereof.
Generally, when pouring fuel such as gasoline into a fuel tank of a car and the like, a fuel inlet 701 as shown in FIG. 31 is used. A connecting pipe J is fixed to the end of the fuel inlet 701 on the fuel tank side, and a breather tube 703 communicating with the fuel tank T is provided in the vicinity of a fuel port 701a of the fuel inlet 701. At the time of fueling, a not shown fuel feeding nozzle is inserted into the fuel inlet 701 through the fuel port 701a and fuel is fed into the fuel tank T through the fuel inlet 701 and the connecting pipe J. When fuel feed into the fuel tank T starts, the air in the fuel tank T is pushed toward the fuel port 701a of the fuel inlet 701 through the breather tube 703. When fuel feed continues and a certain amount of the fuel is stored in the fuel tank T, the internal pressure of the fuel tank T increases and causes the fuel feed nozzle to automatically stop, and further automatic feeding is impossible. A person who feeds fuel notices it and shifts the feeding into manual operation, and additionally pours a small amount of gasoline two to three times before finishing the feeding.
The above process involves a problem that since the air pushed toward the fuel port while the feeding contains a high density of fuel vapor, careless emission thereof into the atmosphere leads to an increase of fuel density around and thus unfavorable effects on the environment.
To solve this problem, it is proposed to employ a fuel inlet 801 shown in FIG. 32. The fuel inlet 801 is provided with a relatively small diameter portion 806 within its fuel passage. Since a space 807 shown in cross section of the passage, when fuel fed at a specific rate passes the relatively small diameter portion 806, is made smaller than in a conventional fuel inlet, venturi vacuum is generated and negative pressure in the space 807 is increased. As a result, the air returning toward the fuel port from the fuel tank through the breather tube 803 is effectively prevented from being emitted into the atmosphere. This is called a liquid seal, which is one of the means in Onboard Refueling Vapor Recovery systems, or ORVRs.
However, if the fuel inlet 801 having a relatively small diameter portion 806 of xcfx8625.4 mm, for example, is produced as a solid one by pressing a blank pipe instead of connecting a plurality of members, one end of the blank pipe of xcfx8625.4 mm, i.e. the fuel port should be expanded to xcfx8648 mm to 60 mm, and such a large expansion often causes cracking. Also it is required that the breather tube 803 and the inlet pipe 802 be connected easily and securely and that a spiral groove be easily formed around the expanded end of the inlet pipe to allow a cap to be screwed thereon.
A fuel inlet, having a double structure in the vicinity of the fuel port formed by folding one end of the pipe inward, is known as disclosed in the Publication of Japanese Unexamined Patent Application No. 9-39591(Cf. FIG. 33B). This type of fuel inlet 901 obtains enough strength because of the double structure in the vicinity of the fuel port and has a great durability against abrasion due to opening/closing operation of the fuel port cap.
The above fuel inlet 901 is formed as follows: Firstly, as shown in FIG. 33A, a first taper portion 901a and a second taper portion 901b are formed. Secondly, the first taper portion 901a and the second taper portion 901b are folded back to the inside of the pipe (See dotted lines in FIG. 33A) by applying pressure P in the axial direction onto the open end of the second taper portion 901b. Then, the folded end is expanded and a groove 901c is formed. By forming the first taper portion 901a and the second taper portion 901b having different cone angles, respectively, and folding these taper portions, the bending region can be prevented from being applied an excessive load thereto.
Although the fuel inlet 901, wherein a double structure is provided in the vicinity of the fuel port by folding back the end of the pipe, is quite useful, it involves a problem that the manufacturing process thereof is complicated. These days a fuel inlet is sometimes provided with a retainer having an interference portion, but it makes the manufacturing process further complicated to produce such an inlet according to the method disclosed in the Publication of Japanese Unexamined Patent Application No. 9-39591. Attaching a separate retainer to the folded end is practical, and a synthetic resin retainer which is usually more expensive than a metal one is fixed in because it is difficult to attach a metal retainer to the folded end by crimping or welding.
Also known is a structure, as shown in FIG. 34, wherein a fuel inlet 1001 is forced and fixed into a fuel inlet supporting hole 1015 provided in a car body B (See Publication of Japanese Examined Utility Model Application No. 6-259, for example). Specifically, the fuel inlet 1001 having a synthetic resin cylindrical cover 1005 fitted on the outer circumference in the vicinity of the fuel port is forced into the fuel inlet supporting hole 1015 from the side of a fuel tank T, thereby the cylindrical cover 1005 is pressed against the fuel inlet supporting hole 1015. Since this structure enables relative movement between the car body B and the fuel inlet 1001, even if a heavy load is applied to the car body B, for example, the car body B yields or bulges independently of the fuel inlet 1001, and therefore the heavy load does not directly affect the fuel inlet 1001. Furthermore, even if the car body B is deformed to bulge toward the fuel inlet 1001, the bulging region does not cause the fuel port cap C to be pushed up and removed because the outer diameter of the fuel port cap C is designed to be smaller than the outer diameter of the cylindrical cover 1005.
The structure in FIG. 34, however, has a problem that the cylindrical cover 1005 made of synthetic resin leads to the higher cost of materials, which makes the cost for fixing the fuel inlet 1001 increased. Also, the cylindrical cover 1005 used as a separate member needs to be produced separately as well as requires another process step of attaching the same to the fuel inlet 1001, and as a result the cost for fixing the fuel inlet 1001 is further increased.
Moreover, this structure requires a retaining mechanism for preventing the cylindrical cover 1005 from being displaced axially relative to the fuel inlet 1001 when the fuel inlet 1001 with the cylindrical cover 1005 wrapped therearound is forced into the fuel inlet supporting hole 1015. Specifically, as shown in FIG. 34, the retaining mechanism is constituted by a bead 1001a provided on the outer circumference of the fuel inlet 1001 and a groove 1005a provided on the internal circumference of the cylindrical cover 1005 for catching the bead 1001a. This type of retaining mechanism complicates the structure of the fuel inlet 1001 and impedes production thereof.
Wherefore, a principal object of the present invention is to provide a fuel inlet which has a liquid seal function and whose production requires only a small number of parts and also is easy.
Another object of the present invention is to provide a fuel inlet which has a double structure in the vicinity of its fuel port and is easy to make.
Further object of the present invention is to provide a fuel inlet having a simple structure and not requiring high cost of fixing the same to a car body such that relative movement is allowed therebetween.
According to the first phase of the present invention, the fuel inlet comprises: an inlet pipe for guiding fuel into a fuel tank and a breather tube for letting the air out of the fuel tank toward the forward end portion of the inlet pipe while feeding fuel, one end of the inlet pipe being expanded to have a diameter one and a half to three times as large as the diameter of the body of the inlet pipe, and also being provided with a spiral groove directly formed therein, for engaging with a cap, an open end of the breather tube joined to the forward end portion of the inlet pipe being provided with a flange, which is projection welded on the area around a hole provided in the forward end portion of the inlet pipe.
The fuel inlet of the present invention is preferably made of a material selected from SUS304, SUS304L, SUS436 according to JIS, and their equivalents.
According to another phase of the present invention, the fuel inlet comprises: an inlet pipe for guiding fuel into a fuel tank; a cylindrical reinforcement overlapping the inner circumference of the inlet pipe in the vicinity of the fuel port thereof; and a screw portion for screwing a fuel port cap thereon formed by crimping the inlet pipe and the cylindrical reinforcement.
According to a further phase of the present invention, the fuel inlet is forced and fixed in a fuel inlet supporting hole provided in a car body such that relative movement between said fuel inlet and the car body is allowed. The fuel inlet comprises: an extending portion extending radially outward from the edge of an inlet pipe on the side where a fuel port cap is screwed; and an outer-cylinder-like flange adjoining the extending portion and having a configuration formed by being folded back in the axial direction of the inlet pipe, the outer-cylinder-like flange being fixed tight in the fuel inlet supporting hole when forced thereinto.
According to a still further phase of the present invention, the fuel inlet having liquid seal function comprises: a relatively large diameter portion formed on the side of a fuel port; and a relatively small diameter portion formed integrally with the relatively large diameter portion on the side of a fuel tank, the relatively small diameter portion having a diameter smaller than the relatively large diameter portion by being provided with a plurality of elongate protrusions having a configuration of being pinched from the outside.